Computational Modeling of Dynamic Electron Paramagnetic Resonance Spectra

Abstract

A comprehensive method is laid out for the solution of the stochastic Liouville equation to simulate spectral lineshapes for continuous-wave EPR spectra. The method is presented in a general fashion so that the same implementation can be used to simulate general spin systems with any number and type of spin Hamiltonian interaction terms. A modification of the frequency-dependent spectral lineshape function to a field-dependent lineshape function is also presented for simulations of systems in which the field-sweep experiment must be accounted for explicitly. Simulations are presented for a S = 1/2 nitronyl nitroxide system with multiple magnetic nuclei and for a S = 7/2 gadolinium(III) system using the general solver over a range of rotational correlation times. CW EPR spectra are also measured for S = 1/2 copper(II)-EGTA over a range of temperatures to show the importance of performing explicit field sweep simulations in the slow-motion regime for spin systems with highly anisotropic g-tensors.